Ray optics
Introduction
Ray optics, also known as geometrical optics, is a branch of optics that describes light propagation in terms of rays. The ray in geometric optics is an abstraction useful for approximating the paths along which light propagates under certain circumstances.
Fundamental Concepts
The primary concept behind ray optics is the light ray, an idealized model of light propagation. Light rays are defined as straight lines that travel in a homogenous medium. They bend at the interface of two different media and may be curved in a medium where the refractive index changes.
Reflection
Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. The law of reflection states that the incident ray, the reflected ray, and the normal to the surface of the mirror all lie in the same plane.
Refraction
Refraction is the change in direction of a wave due to a change in its transmission medium. The phenomenon is explained by the conservation of energy and the conservation of momentum. Due to the change of medium, the speed of the wave is changed, causing the direction of the wave to change.
Dispersion
Dispersion in optics is the phenomenon in which the phase velocity of a wave depends on its frequency. This is most commonly seen when white light is separated into its component colors by a prism.
Applications of Ray Optics
Ray optics is used in many areas of physics and engineering. It is the basis of many optical instruments and devices such as the microscope, telescope, and camera.
Lenses
Lenses are one of the most direct applications of ray optics. They are designed based on the principles of refraction and reflection to focus light, creating an image of an object at a certain location.
Mirrors
Mirrors are surfaces that form images by reflecting light. They can be flat or curved, and their shapes can affect the properties of the images they form.
Optical Instruments
Many optical instruments, including the human eye, are based on the principles of ray optics. These instruments use lenses and mirrors to focus light and create images.
Limitations of Ray Optics
While ray optics provides a simple and powerful tool for understanding many optical phenomena, it has its limitations. It fails to accurately describe phenomena such as diffraction and interference which require the wave nature of light to be taken into account. These phenomena are better described by wave optics.